Irrigation with saline water is a worldwide necessity an excess of salts in water or in soil causes growth inhibition, and negatively affects the productivity of many crops. Application of nitrogen fertilizers may be a way of mitigating the effects of salts on plants. The aim of this study was to evaluate the accumulation of biomass and the chlorophyll pigment content in jackfruit seedlings irrigated with water of increasing salinity level in soil with nitrogen sources. The treatments were distributed in randomized blocks with four replicates and three plants per plot, arranged in a 5 × 3 factorial scheme, related to electrical conductivity levels of the irrigation water of 0.3, 1.0, 2.0, 3.0 and 4.0 dS m^-1, in soil without nitrogen, with ammonium sulfate and with urea, in a split application 60 and 75 days after sowing. An increase in the salinity of the water increased the salinity levels of soil, which was intensified by a dose of 150 mg of N, mainly when applied in the form of ammonium sulfate, inhibiting dry matter production and chlorophyll content in jackfruit seedlings. The greatest reductions in chlorophyll a and b content occurred in jackfruit seedlings irrigated with water of 4.0 dS m^-1 conductivity in the soil without nitrogen fertilization. Urea is the most suitable nitrogen source for the production of seedlings under conditions of high salinity.

Salinity is one of the major obstacles to agriculture in semi-arid regions, as it affects the physiological processes, growth, and yield of numerous crops. Hence, the application of salt stress attenuators is of paramount importance, as it enables the use of saline water for agricultural purposes. Among these, humic acid promotes the growth as well as water and nutrient uptake of plants. To this end, the present study evaluated the effects of humic acid on the growth and physiology of Carica papaya seedlings irrigated with saline water. The experiment followed the randomized block design with five levels of electrical conductivity (0.5, 1.15, 2.75, 4.35, and 5.0 dS m-1) and five concentrations of humic acid (0.5, 0.94, 2.0, 3.06, and 3.5 mL L-1). Growth, gas exchange, chlorophyll content, and chlorophyll a fluorescence were evaluated. Irrigation with 4.9 dS m-1 water and application of 3.05 mL L-1 humic acid promoted the growth of papaya seedlings. Irrigation with high-salinity water (4.96 and 3.09 dS m-1) coupled with the application of 3.05 and 2.21 mL L-1 humic acid increased internal CO2 concentration, transpiration, instantaneous water use efficiency, carboxylation efficiency, and chlorophyll b content. Overall, humic acid (3.5 mL L-1) attenuated the deleterious effects of salt stress, promoting the growth and improving the performance of papaya seedlings under moderate salinity (4 dS m-1).

Soil salinization is a problem commonly found in semi-arid regions. In addition, the problem of salinity is aggravated in clayey soils when accompanied by cycles of waterlogging in the rainy season or when excess irrigation is applied. In this work we evaluated the isolated and combined effects of soil salinity and waterlogging on the responses of young plants of ‘Green Dwarf’ coconut. The experiment was conducted under controlled environment in a complete randomized block design, arranged in split plots with five replications. The plots comprised five waterlogging cycles (0, 1, 2, 3 and 4), each with a duration of four days, and applied at 30, 60, 90 and 120 days into the experimental period, with the sub-plots consisting of five levels of soil salinity (1.70, 11.07, 16.44, 22.14 and 25.20 dS m-1). Response of coconut seedlings to waterlogging was dependent on the level of soil salinity, with waterlogging significantly impairing biomass accumulation and leaf expansion at low soil salinity levels, but causing no additional harm at elevated salinity. Leaf gas exchange was reduced mainly due to soil salinity, and this response was related to stomatal and non-stomatal effects. Seedlings of ‘Green Dwarf’ coconut used in this study were classified as moderately-tolerant to salinity when grown in soils with an electrical conductivity up to 11.07 dS m-1, having the potential to be used in revegetation programs of salt-affected areas, provided that these areas are not exposed to frequent waterlogging cycles.

Biosaline agriculture is an option for using waters with lower quality. Thus, the objective of this study was to evaluate the growth of ornamental species under irrigation with increasing water salinity levels in two methods of water application. The study was conducted in a greenhouse, in the municipality of Fortaleza, Ceará, Brazil. The treatments were distributed in randomized blocks in split plots, with six levels of water salinity in the plots (0.6 - control, 1.2, 1.8, 2.4, 3.0 and 3.6 dS m^-1), two methods of water application in the subplots (localized and sprinkler irrigation) and four ornamental species in the sub-subplots (Catharanthus roseus, Allamanda cathartica, Ixora coccinea and Duranta erecta), with four replicates. Increase in irrigation water electrical conductivity reduced the growth of the studied ornamental species. It was not possible to establish an ideal method for irrigation of ornamental species. Effects of non-localized irrigation on leaf growth were more evident in the species C. roseus and D. erecta, which showed higher specific leaf area.

O maracujazeiro amarelo exerce importância econômica e social no setor agrícola brasileiro, impulsionando o agronegócio de frutas tropicais. A agricultura moderna enfrenta um grande desafio, como a melhoria da qualidade dos produtos colhido e diminuição dos custos de produção, busca-se novas práticas de cultivo, como o uso de insumos orgânicos que sejam eficientes e menos poluentes, podendo substituir parcialmente os adubos sintéticos. Neste contexto, objetivou-se avaliar os efeitos dos biofertilizantes bovino no crescimento e produção de maracujazeiro amarelo, no município de Remígio, Paraíba. O delineamento experimental foi em blocos casualizados, com quatro repetições e seis plantas por tratamento, usando o esquema fatorial 2 × 5, referente a dois tipos de biofertilizantes (comum e enriquecido quimicamente), diluídos em água não salina nas doses percentuais de 0,0; 2,5; 5,0; 7,5; 10%, fornecidos quinzenalmente ao solo, em volume constante de 4 L planta-1. As variáveis analisadas foram diâmetro caulinar, período do transplantio à poda da haste principal e dos ramos laterais, número de ramos produtivos, número de frutos por planta, produção por planta e produtividade. Houve interação significativa entre os biofertilizantes e as doses para as variáveis avaliadas, exceto para o período do transplantio a poda da haste principal. Para o diâmetro caulinar, além da interação doses × biofertilizantes, houve efeito isolado da idade de avaliação. Pelos resultados, os biofertilizantes promoveram o crescimento vegetativo das plantas, mas, não estimularam o aumento nos componentes de produção do maracujazeiro amarelo. A dose de 10% de biofertilizante comum foi responsável por maior produção e produtividade.

EFEITOS DA SALINIDADE DO SOLO E ENCHARCAMENTO SOBRE AS TAXAS DE CRESCIMENTO DE PLANTAS JOVENS DE COQUEIRO-ANÃO-VERDE - DOI: 10.7127/rbai.v11n200612